1. Field of the Invention
The present invention relates generally to systems and methods for controlling the breathing rate of a patient. More specifically, embodiments of the present invention are directed to controlling the application of air pressure (e.g., in a bi-level positive air pressure system) to assist a patient with reducing his/her breathing rate.
2. Description of the Related Art
Hypertension is a significant problem in nearly all western cultures and is an underlying cause for stroke and heart attack. Termed the “Silent Killer,” hypertension affects approximately 1 in 4 Americans, and occurs with even higher prevalence in some European communities. Hypertension is also gaining recognition as a co-morbid factor in obstructed sleep apnea (OSA) patient populations, with recent studies indicating that as many as 80% of patients seeking treatment for OSA may unknowingly suffer from this disease.
Slower breathing has been shown to effectively reduce hypertension.
Indeed, a focus of techniques such as Yoga and Qigong is to slow a person's breathing to effectively relieve stress and lower blood pressure. In recent years, the physiological mechanisms underlying this response have been shown to involve changes in the autonomic nervous system through the following chain of events:                The process of slow breathing requires the autonomic nervous system to make more frequent adjustments in blood pressure.        In response to these frequent changes, the autonomic nervous system becomes more sensitive to BP changes (via the baroreflex).        The baroreflex becomes amplified.        In order to better regulate BP, a readjustment of central neural control occurs by increasing vagal activity and inhibiting sympathetic activity, both of which act to reduce BP.        
Several studies support the idea of using slower breathing to reduce blood pressure in hypertensive individuals. Currently, one device on the market (RESPeRATE by Intercure™ (Fort Lee, N.J.)) is FDA approved for the treatment of hypertension. The RESPeRATE device is designed to act as a breathing “coach” by using audiovisual cues to guide the user to a slower breath rate.
The operation of this device is described, at least in part, in U.S. Pat. No. 5,800,337 to Gavish. Gavish discloses a system for modifying naturally occurring biorhythmic activity by changing at least one “non-frequency” characteristic of input to the user in response to changes in the biorhythmic activity of the user. A focus of Gavish is to effect absolute and relative durations of portions or segments of an overall biorhythmic pattern, such as breathing, independently of changes in the overall frequency of the user's biorhythm being monitored (again, e.g., breathing). The input to the user that is disclosed by Gavish includes audio, visual or tactile cues.
While still other biorhythmic feedback methodologies are known, there is nevertheless a need for different approaches to effect the breathing rate or frequency of a patient to induce, among other things, lower blood pressure, or simply induce improved periods of relaxation.